one association from two

rubyonrails-talk
1

I'm working on a two-to-many relationship that works fine from the child object's perspective but not from the parent's. The imperfect, yet functional code looks like this:

2

dschruth wrote:

I'm working on a two-to-many relationship that works fine from the child object's perspective but not from the parent's. The imperfect, yet functional code looks like this: ------------------------------------------------------------------- class PrimaryTable < ActiveRecord::Base   has_many :secondary_tables_1 ,             :foreign_key => :A_primary_table_id,            :class_name => "SecondaryTable" has_many :secondary_tables_2 ,            :foreign_key => :B_primary_table_id,            :class_name => "SecondaryTable" end

class SecondaryTable < ActiveRecord::Base   belongs_to :A_primary_table,            :foreign_key => :A_primary_table_id,            :class_name => "PrimaryTable"   belongs_to :B_primary_table,            :foreign_key=> :B_primary_table_id,             :class_name => "PrimaryTable" end ------------------------------------------------------------------------------------------

But, I don't want to have two linking fields up *and* two linking fields down. I only want one linking field down. I would like to lump these parent to child relationships into one associated link... doing something like this:

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class PrimaryTable < ActiveRecord::Base   has_many :secondary_tables ,            :foreign_key => :A_primary_table_id,            :foreign_key => :B_primary_table_id,            :class_name => "SecondaryTable" end

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...but only one of the two links (the ones to "B_primary_table") shows up this way.

Using the :finder_sql option to has_many, you'll have to write custom SQL that does an "or" on the two foreign keys.